Star formation suppression and bar ages in nearby barred galaxies

TL;DR

This study uses spectroscopic data from 21 barred spiral galaxies to investigate how bars influence star formation suppression and estimates the ages of bars, revealing a broad range of bar ages and supporting abrupt truncation events.

Contribution

It provides new spectroscopic measurements of star formation deserts in barred galaxies and constrains bar ages, highlighting the impact of bars on star formation history.

Findings

Bar ages range from 0.25 to over 4 Gyr.

Star formation deserts show suppressed activity with abrupt truncation.

Results support sudden cessation of star formation rather than gradual decline.

Abstract

We present new spectroscopic data for 21 barred spiral galaxies, which we use to explore the effect of bars on disk star formation, and to place constraints on the characteristic lifetimes of bar episodes. The analysis centres on regions of heavily suppressed star formation activity, which we term 'star formation deserts'. Long-slit optical spectroscopy is used to determine H beta absorption strengths in these desert regions, and comparisons with theoretical stellar population models are used to determine the time since the last significant star formation activity, and hence the ages of the bars. We find typical ages of approx. 1 Gyr, but with a broad range, much larger than would be expected from measurement errors alone, extending from about 0.25 Gyr to more than 4 Gyr. Low-level residual star formation, or mixing of stars from outside the 'desert' regions, could result in a doubling of these age estimates. The relatively young ages of the underlying populations coupled with the strong limits on the current star formation rule out a gradual exponential decline in activity, and hence support our assumption of an abrupt truncation event.